This invention relates generally to internal combustion engines, and, more specifically, to throttle assemblies including vertically mounted throttle shafts that regulate air intake into the engine cylinders.
Conventional internal combustion engines that, for example, power an outboard motor typically include a plurality of throttle plates mounted to an engine cranckcase to regulate an amount of air delivered to each cylinder of the engine. A throttle linkage typically connects the throttle shafts of the throttle valves to substantially synchronize the position of the throttle plates to stabilize engine operation, and a throttle actuator adjusts the positions of the plates to allow adjustment of airflow into the cylinders.
In one type of throttle assembly, each of the throttle plates is mounted to a throttle shaft rotatably mounted to the throttle body and extending through the throttle body. The throttle body defines a generally cylindrical airflow passage, and the throttle plates are also substantially circular so as to substantially restrict air from flowing through the airflow passage when the throttle plates are in a closed position, thereby allowing a minimum amount of airflow into the cylinders, and to allow a maximum amount of air into the engine cylinders when in a fully open position. See, for example, U.S. Pat. No. 5,992,378. The throttle plate is spring biased toward the closed position, and the throttle actuator opens the throttle plates against the bias of the spring.
In some engines, such as in certain outboard motor systems, it is desirable to mount the throttle shafts vertically instead of horizontally. In such systems, however, it has been observed that lubrication oil and/or other engine fluids tend to pool in the bottom of the cylindrical air passages. The pooled fluid tends to seep along the throttle shaft extending through the throttle body to the outside of the throttle body and drips onto exterior surfaces of the motor. This fluid seepage is undesirable for reasons that are apparent.
In an exemplary embodiment, a throttle assembly for an internal combustion engine includes a throttle body that defines an airflow passage, a throttle shaft rotatably mounted to the throttle body and extending though the airflow passage, a throttle plate coupled to the throttle shaft, and a seal member coupled to the throttle shaft. More specifically, one end of the throttle shaft extends through the throttle body, and a seal member surrounds the throttle shaft between the throttle body and the shaft. The seal member extends into the airflow passage and effectively forms a standpipe extending into the airflow passage for a length sufficient to prevent pooled engine fluids from seeping out of said throttle body along the throttle shaft.
In a further embodiment, the seal member is a bushing that surrounds a vertically mounted throttle shaft and is press fit into the throttle body so that the bushing is partially located between the throttle body and the shaft, and partially located in the airflow passage. The bushing extends upward from the throttle body into the airflow passage, but does not extend to the throttle plate. Therefore, the throttle plate is separated from the bushing and is free to rotate within the airflow passage as the throttle shaft is moved with a throttle actuator.
To accommodate the seal member, the throttle plate includes an outer periphery having a first portion and a second portion. One of the portions is curved and continuous and substantially complementary in shape to the airflow passage, and the other portion is discontinuous relative to the curved portion and, in one embodiment, is substantially flat to provide a clearance for the bushing.
A cost effective, leak proof throttle assembly is therefore provided that is particularly advantageous for outboard motor systems.